Michelle Marsh, 32, of Harrisburg, Pennsylvania, seems like the perfect dieter. If you ran into the 5-foot-1-inch, 103-pound marketing specialist checking food labels for calories in the supermarket or powering through one of her seven weekly workouts, you'd envy her ability to control her intake and burn off any excess, too. But Marsh, who had her first baby nine months ago and is now below her prepregnancy weight ("I'm the tiniest I've ever been!" she says), could be the poster girl for an unrecognized epidemic among women: disordered eating.

No, she doesn't starve herself to an unnatural weight (like anorexics) or throw up daily (like some bulimics), but she doesn't seem to have a healthy relationship with food or her body, either. "I spend about half my time thinking about food and meal planning," she says, although her meals don't require much planning—she usually restricts herself to the same foods every day (oatmeal, brown rice and two small corn tortillas with chicken and a sweet potato). "I weigh myself every morning, and if the scale goes up a pound, I exercise more. If I gained 5 pounds, I'd be very upset."

Sound familiar? It should: Sixty-five percent of American women who responded to a national survey by SELF are disordered eaters. Eating habits that women think are normal—such as banishing carbs, skipping meals and, in some cases, even dieting itself—may actually be symptoms of the syndrome. Although disordered eating doesn't have the lethal potential of anorexia or bulimia, it can wreck your emotional and physical health, says Cynthia Bulik, Ph.D., director of the eating disorders program at the University of North Carolina at Chapel Hill and SELF's partner in the survey. And it's everywhere, afflicting women like your sister, your friend, your coworker—or you.

The online SELF survey garnered responses from 4,000 women ages 25 to 45 to a detailed questionnaire about their eating habits and found that most disordered eaters fall into one or more of six categories. Calorie prisoners are terrified of gaining weight, tend to see food as good or bad and feel extremely guilty if they indulge in something that's off-limits. Secret eaters binge on junk food at home, in the car—wherever they won't be found out. Career dieters may not know what to eat without a plan to follow; despite their efforts, they're more likely than other types to be overweight or obese. Purgers are obsessed with ridding their body of unwanted calories and bloat by using laxatives, diuretics or occasional vomiting. Food addicts eat to soothe stress, deal with anger, even celebrate a happy event; they think about food nearly all the time. Extreme exercisers work out despite illness, injury or exhaustion and solely for weight loss; they are devastated if they miss a session. Like Marsh, who Bulik describes as a calorie prisoner and an exercise addict, many disordered eaters piece together a painful mix of destructive habits. Others may shift between categories over the years, ricocheting from restricting to bingeing to purging, for instance.

Even more frightening, the SELF survey reveals that an additional 10 percent of women suffer from outright eating disorders such as anorexia and bulimia, meaning that a total of 75 percent of all American women—three out of four—eat, think and behave abnormally around food.

And despite the stereotype that eating issues affect mostly young women, SELF found that those in their 30s and 40s suffer from disordered eating at virtually the same rates. No wonder, given that we live in a culture that spawns best sellers with titles such as Skinny Bitch and fetishizes stick-thin, ageless celebs on tabloid shows and websites even as our obesity rate continues to rise. "Dieting is a national pastime for women," says Margo Maine, Ph.D., an eating disorders specialist in West Hartford, Connecticut. "As a society, we don't see the problem."

Indeed, 67 percent of women surveyed (excluding those with diagnosed eating disorders) are trying to lose weight, mirroring the number who are overweight or obese. A few eat nutritiously and exercise moderately. The rest turn to risky tricks: Thirty-five percent use diet pills, 26 percent cut out entire food groups and 13 percent even smoke to slim down, they confessed to SELF.

The result is failure; extreme measures don't work. Just ask career dieter Kathie, 42, a mother of two in Fairfax Station, Virginia, who asked that we not print her last name. Raised in a clean-your-plate house where sweets were locked away in a metal cabinet in the basement, Kathie went on her first diet at age 10. "A neighbor and I tried to see how long we could go without eating," she says. "We lasted three days." Because her access to treats was restricted, Kathie didn't know how to handle them when she got to college. "The freshman 15 was more like the freshman 80," she says. "I inhaled everything." Two decades of dieting followed. "I did the grapefruit diet, the cabbage soup diet, Atkins, everything," Kathie says. "My mother joked that I had my fat closet and my skinny closet, and I could never get rid of my fat clothes. I felt doomed to be fat."

Kathie is finally on the road to a healthy weight, but not due to dieting. She opted for gastric bypass surgery four years ago and has lost 110 pounds. (She weighs 192.) "I'm raising my kids differently," she says. "I put food down, and if they're hungry, they eat it. If not, that's OK. We have cookies out. The last thing I want is for them to battle their weight their whole life."

The fact is, Kathie might never have been able to permanently lose weight by restricting her food intake. "Low-calorie dieting—going below 1,200 a day—can cause your metabolism to slow to a crawl," says Sondra Kronberg, R.D., director of the Eating Disorder Associates Treatment and Referral Center in Westbury, New York. The upshot: You can gain weight on a low-calorie diet because your body will burn off fewer calories and store more of them to protect against starvation.

But not all disordered eaters are obese or even overweight; 53 percent of dieters in our survey are already at a healthy weight and are putting themselves at risk by attempting to change it. "For many women, dieting is about trying to exert control," Kronberg says. Your job may be stressful and your boyfriend halfway out the door, but you can control what you eat and how often you work out. "When a woman who isn't overweight tries to drive her body lower than it wants to go, she could do herself permanent harm," warns Diane Mickley, M.D., director of the Wilkins Center for eating disorders in Greenwich, Connecticut. Without adequate body fat to supply hormones critical to bone health, you can develop an aggressive, irreversible form of osteoporosis as early as your 20s, leaving you with the easily broken bones more common to women in their 70s. Malnutrition can also cause hair loss, brittle nails and even nerve damage.

Dieting can be psychologically harmful, too. How many of us live in a state of misery because of the size of our thighs? A lot: Thirty-nine percent of women say concerns about what they eat or weigh interfere with their happiness. "I exercise every day," says 30-year-old Alisa, who typically runs an hour on the treadmill and lifts weights for 30 minutes. "If I eat dessert, I run 20 more minutes. I don't have time for my family and friends," she says tearfully. "It's an issue I deal with every day."

So does 28-year-old Patricia of Nashville, who shuns trendy clothing and covers up in modest outfits because she's embarrassed by her body. At 5 feet 8 inches and 178 pounds, she admits her overeating pushed her to try laxatives, skip meals and fast, all to no avail. She gave up laxatives because they didn't keep the pounds off, but Patricia still overeats sometimes, usually fast food. "I don't want anyone to see me," she says. So she hits a drive-through, eating two cheeseburgers, fries and a Coke in her car in minutes. "I'm numb while I do it, and I feel guilty afterward," she says. "I think about food 20 percent of the time." Four percent think about it nearly every waking moment. "Imagine what women could accomplish if they spent that time and energy on things other than body issues," Bulik says.

But if you're dieting, you can't think about anything else. "Dieting causes you to obsess about food by altering serotonin levels in the brain," says Timothy D. Brewerton, M.D., clinical professor of psychiatry and behavioral sciences at the Medical University of South Carolina in Charleston. "Diets around 1,000 calories may cause symptoms of depression, such as low sex drive, irritability, anger and social withdrawal." But even moderate-sounding plans can make you miserable. When Yolanda Castellini, 31, of Clarksville, Tennessee, goes below 1,400 calories a day, "I get physically ill," she says. "But I'm always on a diet." At 5 feet 6 inches and 155 pounds, Castellini is just barely overweight but firmly in the calorie-prisoner category. "It's a cycle," Dr. Brewerton says. "Women diet to feel and look better, but they inadvertently make themselves feel worse."

Even skipping a meal—something 37 percent of the women surveyed do regularly to try to lose weight—can cause emotional symptoms within hours. More worrisome, withholding calories can lead to another disordered behavior: repeated binges. Everybody has inhaled too many cookies at one sitting now and then. While not exactly healthy, scarfing whatever's in reach when your blood sugar is low isn't technically a binge. What is? Eating an unusually large amount of food quickly and feeling out of control while doing it. One in four women binge. "I do it when I feel rejected, especially in love," says Rochelle, 41, a teacher in New York City. "I've gone from one pizzeria to another, eating slice after slice and worrying whether there were hidden cameras that would record my eating. I'll eat until I feel sick."

"Bingers eat instead of dealing with their feelings," says Kathryn Zerbe, M.D., professor of psychiatry at the Oregon Health & Science University in Portland. Jamie, a 31-year-old in Bremerton, Washington, doesn't know what used to push her to overeat. "My son would be playing, my daughter napping and my husband wasn't home—that's when I'd do it," says the stay-at-home mom. "An entire cake would be gone. I'd feel horrible afterward and wouldn't eat for the rest of the day. I never got on a scale because I didn't want to know how much I gained." Even though she gradually began to eat healthier and lost 34 pounds, "I could eat a cake right now," she confesses.

Despite her struggle, Jamie is lucky. Often, bingeing causes weight gain and anxiety, in turn leading to calorie restricting, fasting and purging. Even frequent overeating, if not technically bingeing, is risky. "If you habitually push past your satiety boundary, you lose touch with your internal stop signs," Bulik says, possibly putting you on the road to bingeing and restricting.

The survey also found glimmers of hope in women such as Amey Cramer, 27, of Orrtanna, Pennsylvania, who weighs 210 pounds and says she's a former food addict. "I used to eat anything I wanted," she says. "I'd eat when I was happy, sad; it didn't matter. I felt awful all the time, and one day I realized I can't do this anymore. I've made little changes—exercising three times a week—and already lost 15 pounds," she says. "I still eat chocolate, but in smaller amounts, and I use olive oil instead of butter. Now I think life is great." That's a happy mind-set we can all aspire to.